In the manufacture of recycle pellets for use as nuclear fuel in light water and breeder reactors, it is necessary to process large quantities of highly radioactive powders. These processes typically involve the mixing of fissile material (i.e., material containing elements which can undergo fission) with fertile material (i.e., material containing elements capable of becoming fissile). These powders must be mixed in precise proportions to maintain the proper fissile content of the pellets. After mixing, the pellets are fabricated, sintered, and ground to the proper tolerances.
Because pellet manufacture involves such highly radioactive materials, the processing must be done by remote control in a protective canyon, which greatly adds to the difficulty and expense of the manufacturing procedure. In addition, because fine powders are being processed, a dust is produced which clings to and coats the walls and manufacturing equipment. Since some of this dust can contain plutonium, which can be used for making bombs, it is difficult to account for all the plutonium involved in the process in order to insure the nonproliferation of nuclear weapons. Also, because the powder adheres to the processing equipment, it is difficult to produce fuel having different specifications because the powder remaining in the equipment tends to contaminate new powders processed in the equipment. Still another difficulty is the tendency of submicron powders of different chemistries to segregate during blending and during pneumatic transport which results in the production of inhomogeneous pellets.